A control apparatus of this type usually includes at least two control members for controlling various functions of the installation. In general, the apparatus has several control members, for adjusting, respectively, the temperature of the air delivered into the cabin of the vehicle, the speed of an air blower, and the distribution of the air through the various outlet vents arranged within the cabin. A member may also be provided for controlling the ratio between the flow of air from outside the vehicle and the flow of recirculated air, i.e. air which is drawn from within the cabin and then delivered back into the cabin after being treated. In addition, if the vehicle is equipped with an air conditioning option, an air conditioning control member is also provided.
These various control members generally consist of rotary knobs, or push buttons, or sliding cursor control knobs, with each type of button corresponding to a given function. Such control elements are of known, standardized types.
The number and type of control members fitted in the fascia of the vehicle depends of course on the number of options chosen. In consequence, the housing that contains the control members together with the associated circuits, which may be mechanical, pneumatic, electrical and/or electronic, is designed to suit the control members that are selected for a given model of vehicle.
It is also necessary to adapt the housing, firstly in accordance with the size of the fascia, and secondly having regard to the space available behind the latter. As a result, in current practice the housing for the control apparatus is specific to a given model of vehicle in most instances. Only rarely can it be used in a number of different models. This situation gives rise to substantial increases in selling price.